The present invention relates to the diagnosis of Candida vaginosis. In particular, the invention concerns the presumptive detection of Candida in vaginal fluid by means of a chemical assay.
Candida albicans and related species can inhabit mucocutaneous body surfaces and are considered endogenous anorectal flora. Vaginal infections caused by Candida sp. occur due to changes in vaginal ecology brought on by an increase in estrogen, as may occur during premenses, pregnancy, oral contraception, treatment with broad spectrum antibiotics or treatment with steroids. Also, women with immune dysfunction, diabetes or multiple sexual partners are at an increased risk of developing Candida-caused vaginitis. In these instances, this normal mucocutaneous commensal may overgrow the predominant Lactobacillus flora of the vagina and cause "candida vaginitis," also known as vaginal candidosis. This localized infection is the most commonly reported genital infection in women attending genitourinary medicine and sexually transmitted disease clinics (Laboratory Methods for the Diagnosis of Sexually Transmitted Diseases; Eds. B. Wentworth and F. Judson, Am. Pub. Hlth. Assoc., Washington, D.C., 1987).
Although effective treatment of Candida-caused vaginitis relies on making an accurate diagnosis, treatment of a patient is often based simply on the patient's verbal description of the malady or symptoms. Whereas a physical examination may reveal the classic discharge described as the consistency of cottage cheese, patients many times do not present with classic symptoms. Additionally since vaginal infections may have other microbial etiology, there is need for alternative approaches to differential diagnosis, i.e., in addition to patient symptoms and physical examination. Since diagnosis is generally made during an office visit, simple methods are needed to enable rapid confirmation of clinical information. Methods currently in place in physicians' clinics to provide differential diagnosis of vaginal infections include measurement of vaginal pH, microscopic examination of Gram stains and potassium hydroxide (KOH) wet mounts, and KOH generation of an amine odor. The diagnosis of Candida-caused vaginitis generally is made on the basis of a 10% KOH smear with identification of pseudohyphae (yeast). In most cases, the quantity of yeast is higher in vaginal fluid from patients with a Candida vaginitis than in fluid from asymptomatic women colonized by Candida. Unfortunately, with a reported level of only 38% correlation of microscopy with correct diagnosis (R. Rajakumar, et al., Use of Slide Latex Agglutination Test for Rapid Diagnosis of Vaginal Candidosis, Genitourin. Med. 63:192-195, 1987), microscopy is a relatively poor aid to the diagnosis o Candida vaginitis.
The molecular characteristics of Candida antigens present in tissue and serum during systemic invasion of the body by Candida (a medical condition known as candidiasis or candidosis) are well reported in the literature. (C. Lemieus, G. St-Germain, et al., Collaborative Evaluation of Antigen Detection by a Commercial Latex Agglutination Test and Enzyme Immunoassay in the Diagnosis of Invasive Candidiasis, J. Clin. Microbiol. 23:249-253, 990; L. Zoller, I. Kramer et al., Enzyme Immunoassays for Invasive Candida Infections: Reactivity of Somatic Antigens of Candida albicans, J. Clin. Microbiol. 29:1860-1867, 1991; R. Matthews and J. Burnie, Diagnosis of Systemic Candidiasis by an Enzyme-Linked Dot Immunobinding Assay for a Circulating Immunodominant 47-Kilodalton Antigen, J. Clin. Microbiol. 26:459-463, 1988). However, a comparatively small amount of research has been conducted to identify Candida antigens present in vaginal fluid of patients with Candida vaginitis. Recently, however, several immunoassays have been developed for Candida vaginitis diagnosis. For example, Mercia Diagnostics Ltd., Surrey, UK, has commercialized an immunoassay which employs Candida-reactive antibody-coated latex beads; the beads agglutinate (appear as visible clumps) when a suspension of the latex beads are brought into contact with Candida antigens present in vaginal fluid. Although latex agglutination assays are relatively simple to perform, their poor cost/benefit ratio has minimized their use, i.e., diagnosticians consider test cost too high for the diagnostic benefit they pose. A number of the immunoassays are based upon detection of Candida cell wall mannan (W. J. Pike, J. Clarke et al., Candida Cell Wall Mannan in the Vagina and its Association with the Signs and Symptoms of Vaginal Candidosis. J. Med. and Vet. Mycol. 29:305-312, 1991).
Studies of systemic or invasive Candida infection have shown that D-arabinitol is a major metabolite appearing in urine and serum (J. M. Jones, Laboratory Diagnosis of Invasive Candidiasis, Clin. Microbiol. Rev. 3:32-45, 1990) It has also been shown that the serum and urine levels of this metabolite depend on the efficiency of its production by yeast during the systemic infection and on the mode and rate of elimination of the metabolite by the host (E. Bernard et al, Rate of Arabinitol Production by Pathogenic Yeast Species, J. Clin. Microbiol. 14:189-194, 1981). See also J. W. Gold et al, Serum Arabinitol Concentrations and Arabinitol/Creatinine Ratios in Invasive Candidiasis, J. Infect. Dis. 147:504-513, 1983. D-Arabinitol in the sera of patients with candidiasis has been measured by gas-liquid chromatography (T. E. Kiehn et al, Candidiasis: Detection by Gas-Liquid Chromatography of D-Arabinitol, a Fungal Metabolite, in Human Serum, Science 206:577-580, 1979) and by enzymatic assay with D-arabinitol dehydrogenase (K. Soyama and E. Ono, Enzymatic fluorometric method for the determination of D-arabinitol in serum by initial rate analysis, Clin. Chim. Acta 149:149-154, 1985; and B. Wong and K. L. Brauer, Enantioselective Measurement of Fungal D-Arabinitol in the Sera of Normal Adults and Patients with Candidiasis, J. Clin. Microbiol. 26:1670-1674, 1988).
Arabinitol has also been reported to appear in the urine of diabetic and uremic patients (E. Pitkanen, Clin. Chim. Acta 38:221-230, 1972), although it may be that such appearance of arabinitol was due to low grade Candida infections in the patients studied.